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Departments of Anaesthesiology and Critical Care, Harvard Medical School; Anesthesia Services, Massachusetts General Hospital; and Shriners Burns Institute, Boston, Massachusetts 02114
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Nosek, M. T., and J. A. J. Martyn.
Na+ channel and acetylcholine
receptor changes in muscle at sites distant from burns do not simulate
denervation. J. Appl. Physiol. 82(4):
1333-1339, 1997.
Muscle weakness and aberrant responses to
neuromuscular relaxants after burn injury are associated with
upregulation of acetylcholine receptors (AChRs). Typically, these
functional, pharmacological, and biochemical changes occur after
denervation, in which transcriptionally mediated qualitative changes in
AChRs and Na+ channels and of
myogenic regulatory proteins MyoD and myogenin also occur. This study
in rats, by an examination of changes in the above-enumerated proteins
or their transcripts in the gastrocnemius muscle distant from the burn,
verifies whether a denervation-like state exists after burns. Scatchard
analysis of
[3H]saxitoxin binding
revealed no changes in the affinity
(Kd) and total
number (Bmax) of
Na+ channels between control and
burn-injured animals at both 7 and 14 days after injury. The mRNA
levels of the immature proteins, SkM2 of the
Na+ channels and the 
-subunits
of AChRs, the increase of which is pathognomic of denervation, were
assessed by Northern analysis and were unchanged. The transcripts of
mature Na+ channels, SkM1, were
significantly increased at day 14 after the burn (1.24 ± 0.10 in burn-injured vs. 1.06 ± 0.12 in
sham animals, arbitrary units, P = 0.006). Although MyoD levels were increased in burn-injured
animals at 14 days (0.21 ± 0.02 vs. 0.15 ± 0.07 arbitrary
units, P = 0.05), myogenin levels were
unaltered. The absence of changes in AChR transcripts, including 
-,
-, and -subunits, indicates that the upregulation of AChR in
burns is not transcriptionally mediated. The unaltered levels of
transcripts of myogenin, SkM2 of
Na+ channels and -subunit of
AChR, confirm that there is no denervation-like prejunctional
(nerve-related) component to explain the muscle weakness or the
upregulation of AChRs at sites distant from burns.
acetylcholine receptors in burns; sodium channel in burns; muscle
weakness in burns; transcripts of muscle receptors in burns
INTRODUCTION BURN INJURY AND OTHER FORMS of critical illness are
associated with functional and pharmacological changes in the skeletal muscle. The pharmacological changes include a lethal hyperkalemic response to the depolarizing relaxant succinylcholine and resistance (hyposensitivity) to nondepolarizing relaxants, typified by
d-tubocurarine (8, 10, 12, 13, 18,
30). Upregulation (increase) of skeletal muscle nicotinic acetylcholine
receptors (AChRs) accounts for some of the pharmacological responses in
burns and is observed even at sites distant from the burn (8, 10, 18).
The molecular mechanism of this upregulation of AChRs has not been
established for burn injury. An important functional change, even at
sites distant from the burn, is muscle weakness, which results in
decreased mobilization, ventilatory failure, and difficulties in
weaning from the respirator (7, 12, 22, 23, 32). The relationship of
muscle paralysis or weakness after burns to the upregulation of AChRs
is unknown. In the pathological states of upper or lower motor neuron
injury, immobilization, and also during development, increased AChRs
and muscle weakness occur concurrently (12, 27-29). It is unclear,
however, whether the upregulation of AChRs associated with burn injury,
although smaller in magnitude, is similar to that seen in the above
states, in which the upregulation of AChRs is transcriptionally
mediated and is also associated with de novo synthesis of additional
proteins (see below).
In addition to other proteins, the innervated muscle membrane consists
of "mature" AChRs containing The purposes of the study were 1) to
test whether the upregulation of AChRs at sites distant from the burn
injury was transcriptionally mediated (as seen with denervation) and
2) to examine if qualitative changes
in AChRs and Na+ channels do
occur. Qualitative changes, if present, may explain some of the
functional changes in muscle occurring with burns. Changes in
Na+ channels were studied by
saxitoxin (STX) binding and by measurement of transcripts of SkM1 and
SkM2. The measurements of transcripts of METHODS
-, 
-, -, and 
-subunit proteins. During development or with denervation of motor nerve, the
gene for the "immature" AChRs is activated, and these AChRs become incorporated in the perijunctional area and throughout the
muscle membrane (13, 28). In the immature AChRs, the -subunit instead of the -subunit is expressed, together with the usual -,
-, and -subunits (13, 28). Also during development and after
denervation, in addition to the usual mature isoform (SkM1) of the
Na+ channel, an immature isoform
of the Na+ channel (SkM2) is
expressed de novo on the muscle membrane, (1, 9, 31).
Electrophysiological (functional) and pharmacological properties of the
immature AChRs and immature Na+
channels differ from those of the mature isoforms (9, 17, 19, 24, 28,
31). The altered electrophysiological characteristics in the immature
isoforms of AChRs and Na+ channels
seem to be related to the improper channel
sensitization/desensitization (1, 5, 6, 24, 28). Thus qualitative
and/or quantitative changes of AChRs and
Na+ channels similar to those seen
with partial or complete denervation, if present after burns, may play
a role in the muscle weakness after this critical injury. Another
hallmark of denervation is the increased expression of myogenic
regulatory proteins, MyoD and myogenin (4, 29). These regulatory
proteins play a role in transcriptional regulation of AChRs.
-, -, -, and
-subunits of AChR, and of the myogenic regulatory proteins MyoD and
myogenin, additionally verified whether the upregulation of AChRs and
muscle weakness of burns were transcriptionally mediated and were
related to a denervation-like, nerve-mediated phenomenon. These
biochemical changes after burn injury were examined in the
gastrocnemius muscle, a muscle distant from the site of injury. Our
results indicate that, unlike denervation, burn injury does not lead to
expression of the immature SkM2- and -subunit-containing isoforms of
the Na+ channels and AChRs,
respectively. STX binding experiments confirmed the absence of
qualitative changes in Na+
channels. It is unlikely, therefore, that qualitative alterations in
the Na+ channels and AChRs, at
sites distant from the burn, contribute to profound muscle weakness
that complicates severe burn injuries. Additionally, the upregulation
of AChRs at sites distant from the burn is also not transcriptionally
mediated.
80°C until used. Animals whose tissues were
excised at 14 days received a splenectomy under anesthesia 7 days
before burn or sham burn.
-2-ethanesulfonic acid (HEPES), 2 benzamidine, 0.1 benzathonium HCl, and 0.1 phenylmethylsulfonyl fluoride, as well as 0.02% sodium azide and 0.5 mg/ml bacitracin. The pH was adjusted to 7.4 at 4°C. The homogenate
was filtered through a single layer of 0.105-µm nylon mesh. Total
[3H]STX (DuPont/NEN,
Boston, MA) binding was measured over a concentration range of
0.125-50 nM. Nonspecific binding was determined in the presence of
5 µM unlabeled STX (Calbiochem, La Jolla, CA) and was
subtracted from the total binding to determine specific binding. Data
were expressed in ficomoles
[3H]STX bound per
milligram of homogenate protein. Protein was determined by the Lowry
method (11). The total number of
Na+ channels
(Bmax) and affinity coefficient
(Kd) were
calculated from Scatchard plots by linear regression by using
CricketGraph III (Computer Associates, Garden City, NY). Statistical
analyses were performed by using the RS1 program (BBN Software
Products, Cambridge, MA).
RNA extraction and hybridization.
RNA was extracted by an acid/phenol extraction method (2). Briefly,
tissues were homogenized in 4 M guanidine thiocyanate, 25 mM sodium
citrate (pH 7.0), 0.5% sarkosyl, and 0.1 M -mercaptoethanol. A 1:10
volume of sodium acetate (2 M, pH 4.0) was added. The homogenate was
extracted with an equal volume of phenol-chloroform-isoamyl alcohol
(25:24:1; pH 5.2). Samples were centrifuged at 10,000 g, and the aqueous layer was removed
into a clean tube and precipitated with an equal volume of isopropanol
at 20°C. After centrifugation, the RNA pellet was washed
with 75% ethanol. The pellets were resuspended with 5 ml of 4 M
guanidine thiocyanate solution plus 0.5 ml sodium acetate and
precipitated with 5 ml of isopropanol. Pellets were washed and dried as
above and resuspended with diethylpyrocarbonate-treated H2O. The RNA concentrations were
determined by measuring the 260-nm optical density
(OD260) (1 OD = 40 µg/ml). The
OD260-to-OD280 ratio
(OD260 /OD280)
was determined as an indication of RNA purity.
Northern blot hybridizations were carried out as described previously
(26). Equal amounts (20 µg) of RNAs were separated in a 2%
formaldehyde-agarose gel and transferred to MagnaCharge (Micron
Separations, Westboro, MA) nylon membrane filters. Na+
channel transcript levels were determined by hybridization with antisense RNA probes specific to the SkM1 and SkM2 Na+
channel types (provided by Dr. Roland G. Kallen, University of Pennsylvania, Philadelphia, PA). Probes were prepared with the T3 and
T7 DNA-dependent RNA polymerases (Promega, Madison, WI). All other RNA
levels were determined by using random oligonucleotide-primed cDNA
probes prepared with the Prime-It II kit (Stratagene, LaJolla, CA). The
probes for the AChR subunits MyoD and myogenin were used in our
previous studies (26). The GAPDH probe was a human cDNA sequence
(obtained from Dr. Maria Alexander-Bridges, Massachusetts General
Hospital, Boston, MA). The -actin cDNA was obtained from rat muscle
RNA by reverse transcription polymerase chain reaction (PCR) by using
an RNA PCR kit (Perkin-Elmer, Norwalk, CT). The cDNA, prepared with
oligo(dT), was amplified with the primer pair 5-GGTCTCACGTCAGTGTACAGG-3 and
5-CCGCAAATGCTTTAGGC-3. The amplification product was the
predicted size (~660 base pairs) and had an endonuclease restriction
pattern consistent with the published -actin DNA sequence (16). For
quantitation of RNA levels, autoradiographs were scanned by using a
ScanMaker II scanner (Microtek, Redondo Beach, CA) or Adobe Photoshop
3.0 (Adobe Systems, Mountain View, CA). The images obtained were
analyzed by using National Institutes of Health Image 1.47 software
(NTIS, Springfield, VA).
Statistical analysis.
Comparisons were made, wherever appropriate, to day
0 values (for weights) or to time-matched control
animals (for ion channels and/or their transcripts). The paired
t-test was used for intragroup comparisons and the unpaired t-test
for between-group comparisons. A P < 0.05 was considered significant.
RESULTS
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) and burn-injured (
) groups.
B: Scatchard plots of sham-treated
() and burn-injured () saturation binding experiments. No change
in total number (Bmax) or
affinity (Kd)
was apparent. Data are means ± SD;
n = 9 sham-treated and 8 burn-injured
animals.
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-actin, used commonly for
normalization of the mRNA levels of interest (9, 28), were also
determined. GAPDH levels were not different between groups at
day 7, but at day 14 the mRNA levels of GAPDH were 20% higher in the
experimental group (Table 3). In contrast
to GAPDH, no observable changes in the levels of -actin transcripts
were detected at either time after injury (Table 3). Thus -actin
rather than GAPDH was more appropriately used for normalization of the
Northern blot hybridization data.
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-actin. At
7 days after burn injury, no differences in SkM1 mRNAs were observed.
At 14 days, however, an increase of 17%
(P = 0.0046) in the level of SkM1 transcripts was observed for the burn group relative to sham controls (Table 3).
Levels of transcripts of AChR subunits and myogenic transcription factors. At 7 days, the
- and -subunit transcripts of AChRs did not show
any changes between the sham and burn groups (Table 3). The - and
-subunits of AChRs were not measured at day
7. At day 14, there
was a significant increase in the level of the -subunit of the AChR
only, with no changes observed in the -, -, or -subunit mRNAs
(Table 3). The absence of changes in the transcripts of the -subunit
of AChR at 14 days is shown in the autoradiographic scan (Fig.
3). The expression of the -subunit in
the denervated-muscle sample (positive control) shown in Fig. 3
confirms the ability of our probe to detect the -subunit
transcripts. The contralateral undenervated side did not show changes
in the -subunit. The levels of -subunit mRNA were low and
inconsistently detected at 7 and 14 days in both experimental and
control groups. The changes in myogenic regulatory protein mRNAs were
disparate; no change in myogenin with an increase in MyoD was observed
at 14 days (Table 3). Changes in MyoD and myogenin transcripts were not
measured at day 7.
-acetylcholine receptor (AChR)
RNA level. RNA samples from S and B animals were analyzed by Northern
blot hybridization for 14-day study group. RNA samples from D and DC
were used as positive and negative controls for hybridization,
respectively. Denervation (D) causes increased expression of
-subunit mRNA levels. Such changes were not apparent in DC, S, or
B.
DISCUSSION
The myopathy or muscle weakness of critical illness, including burns, is a serious clinical problem affecting mobilization and ventilation (7, 12, 23, 27, 32). A concomitant biochemical finding in these pathological states is the upregulation of AChRs, which results in a lethal hyperkalemic response to depolarizing relaxant succinylcholine and resistance to the nondepolarizing relaxants such as d-tubocurarine (8, 10, 12, 13, 18, 30). The molecular mechanism of the increase in AChRs after burns has not been elucidated. Although there is no obvious denervation of the motor nerves supplying the affected muscles, different reports have implicated neural, neuromuscular, junctional, and postjunctional factors in the etiology of this muscle weakness (7, 12, 23, 27, 32). After depolarization of AChRs by acetylcholine, propagation of muscle action potentials occurs along voltage-dependent Na+ channels on the muscle membrane. Abnormal electrophysiological Na+ channel function due to qualitative and quantitative changes underlies several skeletal muscle disorders causing muscle weakness (1, 17, 19, 24). These disorders are brought about by abnormal channel modulation, membrane excitability, and/or improper sensitization or desensitization. Therefore, a quantitative decrease in the number of Na+ channels may result in decreased conduction of action potential generated by AChRs. Alternatively, qualitative changes in Na+ channels, for example, expression of immature SkM2, which is expressed after denervation, may contribute to muscle weakness of burns because immature Na+ channels (containing SkM2) have altered channel properties including open channel times and resensitization patterns (1, 17, 19, 24).
In addition to electrophysiological properties, the STX ligand binding characteristics also differ between the two Na+ channel isoforms SkM1 and SkM2. The toxin-sensitive form is expressed with innervation and the insensitive (resistant) form with denervation (9, 17, 31). This pharmacological property of altered toxin binding to muscle membrane was used in our study to assess qualitative and quantitative changes in Na+ channel protein. The absence of qualitative change in Na+ channels is suggested by the Scatchard plot of STX binding, which showed a single binding site (straight line) with no change in Kd. The measurement of mRNA levels of SkM2 confirmed the absence of this isoform at the level of transcription. These experiments (Scatchard analysis and measurements of SkM2 transcripts) thus confirmed the absence of denervation. The identification of SkM2 isoform in our experiments of denervation (Fig. 2, top and bottom) confirmed the ability of the RNA probe to detect such transcripts.
The transcripts of SkM1 were elevated at day
14 after the burn by 17% relative to sham-injured
animals. The Bmax of SkM1 protein itself was also elevated in the burn group by 11%, which did not reach
statistical significance. At first glance, this may seem incongruous,
but it may also suggest that part of the increase in steady-state SkM1
RNA level resulted in an increase in SkM1 protein. Any disparity
between RNA levels and STX binding may be related to inefficient
translational mechanisms or to a burn-mediated increase in turnover of
existing receptors. Furthermore, these results do not rule out the
possibility that burn injury may alter regulation of
Na+ channel function in the mature
SkM1 itself through posttranslational modifications. The
Na+ channel has adenosine
3,5-cyclic monophosphate (cAMP)-dependent phosphorylation
sites. Improper phosphorylation of
Na+ channels, not detectable by
changes in Kd to
STX, can alter amplitude and decay current and can affect muscle
function (15, 21). Regardless, the increases in SkM1 transcripts do not
explain the muscle weakness associated with burn trauma.
Another characteristic of denervation is the specific manifestation of
-subunit-containing AChRs in the corresponding muscle, reflected as
increased expression of its transcripts (28). Although some or all of
other transcripts of AChRs (, , , and ) increase, the
pathognomic biochemical indicator is the expression of
-subunit-containing AChRs (13, 28, 29). Thus examination of the
quantitative changes in the aforementioned transcripts allowed us to
test whether a denervation-like phenomenon occurs after burns to
account for the muscle weakness and associated upregulation of AChRs.
Our study did not detect differences in the -subunit mRNA levels between experimental groups at 7 days (Table 3) and 14 days (Fig. 3)
after the burn. At 14 days, the autoradiographic images for the
-subunit were too faint to scan and analyze in both burn-injured and
control animals. The ability of the probe to detect -subunit of AChR
was, however, confirmed by the strongly positive Northern blot of this
transcript after denervation (Fig. 3).
Motor nerve denervation also results in the increased expression of
myogenic regulatory proteins MyoD and, more consistently, myogenin (4,
29). Compared with MyoD, myogenin is more consistently and dramatically
elevated after denervation (4, 29). The lack of changes in myogenin
confirms the absence of a denervation-like phenomenon
after burns. This finding is consistent with previous preliminary
observations after burns in which myogenin was not altered (26). The
MyoD mRNA levels, however, were increased and contrast with the
previous observation. The reason for this difference is unclear and may
be related to the different "housekeeping" transcripts that were
used to normalize the measured transcripts. In the previous study, all
densitometric values of mRNA levels were expressed as relative
absorbance of the signal to GAPDH mRNA. In the present study, we
observed that GAPDH levels change after burns and, therefore, were not
a good marker for normalization (Table 3). In contrast, -actin
levels did not change and were used in the present study. The single
finding of increased MyoD levels suggesting denervation should be
interpreted in the context of other evidence already described,
pointing to the absence of it.
The measurement of transcripts of -, - and/or
-subunits of AChR at 7 days and/or 14 days also provides an
insight into the molecular mechanism of upregulation of AChRs in burns.
Only the -subunit of AChR protein showed increased mRNA levels.
These findings are consistent with previous observations of increased transcripts of one subunit only (26) and confirm that the increase of
AChRs after burns is probably not transcriptionally mediated. Enhanced
assembly and surface expression of AChRs can occur with increased
levels of cAMP in muscle (3, 20). Burn injury is associated with
increased cAMP levels in muscle, the magnitude of which is related to
size and location of burn injury (22, 23). It seems, therefore, that
the increase of AChRs at sites distant from burns is probably not
related to a transcriptional phenomenon but to a posttranscriptional
mechanism, such as increased assembly and cell surface expression of
the receptor subunits. Nuclear run-on experiments should confirm a lack
of transcriptional control.
In summary, the salient findings of this study are the absence of
increased mRNA levels of -subunit of AChR and of SkM2 of Na+ channels, both of which
exclude a denervation phenomenon. The binding of STX to
only one site, tested by Scatchard analysis, confirms the absence of
SkM2. The lack of change in myogenin transcripts also confirms the
absence of a denervation phenomenon. These findings together, therefore, indicate that there is no denervation
phenomenon or a prejunctional (nerve) component to explain the muscle
weakness and the upregulation of AChRs at sites distant from burns. The absence of changes in subunit transcripts of other measured subunits of
AChR (except -subunit) confirms that the upregulation of AChRs in
burns is posttranscriptionally mediated. This speculation could be
tested in future studies by the administration of adenylate cyclase
agonists (e.g., forskolin), which would increase cAMP further and cause
increased surface expression of existing subunits. Studies are also in
progress to determine whether burn injury causes a denervation-like
state in areas immediately beneath the area of burn. Such differences
in responses between muscles may exist in view of the observation that
the upregulation of AChRs in the muscle beneath the burn was more
profound and the magnitude similar to that of denervation compared with
that observed at sites distant from burns (18).
ACKNOWLEDGEMENTS
This study was supported by National Institute Grants GM-31569-14 and GM-55082-01 (J. A. J. Martyn) and by the Shriners Burns Institute.
FOOTNOTES
Address for reprint requests: J. Martyn, Dept. of Anesthesia, Massachusetts General Hospital, 32 Fruit St., Boston, MA 02114.
Received 19 March 1996; accepted in final form 26 November 1996.
REFERENCES
| 1. | Catterall, W. A. Structure and modulation of Na+ and Ca2+ channels. Ann. NY Acad. Sci. 707: 1-19, 1993. [Medline] . |
| 2. | Chomczynski, P., and N. Sacchi. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal. Biochem. 162: 156-159, 1987. [Medline] . |
| 3. |
Claudio, T.,
A. F. Ross,
and
W. N. Green.
Acetylcholine receptor assembly is stimulated by phosphorylation of its -subunit.
Neuron
7:
659-666,
1991.
[Medline]
.
|
| 4. |
Eftimie, R.,
H. R. Brenner,
and
A. Buonanno.
Myogenin and MyoD join a family of skeletal muscle genes regulated by electrical activity.
Proc. Natl. Acad. Sci. USA
88:
1349-1353,
1991.
|
| 5. | Engel, A. G., E. H. Lambert, D. M. Mulder, C. F. Torres, K. Sahashi, T. F. Bertorini, and J. N. Whitaker. A newly recognized congenital myasthenic syndrome attributed to a prolonged open time of acetylcholine-induced ion channel. Ann. Neurol. 11: 553-569, 1981. . |
| 6. | Gomez, C. M., B. B. Bhattacharyya, P. Charnet, J. W. Day, C. Labarca, R. L. Wollman, and E. H. Lambert. A transgenic mouse model of slow-channel syndrome. Muscle Nerve 19: 79-87, 1996. [Medline] . |
| 7. | Helm, P. A., G. Pandian, and E. Heck. Neuromuscular problems in the burn patient: cause and prevention. Arch. Phys. Med. Rehabil. 64: 451-453, 1985. . |
| 8. | Hogue, C. W., M. S. Itani, and J. A. J. Martyn. Resistance to d-tubocurarine in lower motor neuron injury is related to increased acetylcholine receptors at the neuromuscular junction. Anesthesiology 73: 703-709, 1990. [Medline] . |
| 9. | Kallen, R. G., Z.-H. Sheng, J. Yang, L. Chen, R. B. Rogart, and R. L. Barchi. Primary structure and expression of a sodium channel characteristic of denervated and immature rat skeletal muscle. Neuron 4: 233-242, 1990. [Medline] . |
| 10. | Kim, C., J. A. J. Martyn, and N. Fuke. Burn injury to trunk of rat causes denervation-like responses in the gastrocnemius muscle. J. Appl. Physiol. 654: 1745-1751, 1988. . |
| 11. |
Lowry, O. H.,
N. J. Rosebrough,
A. L. Rarr,
and
R. J. Randall.
Protein measurement with the Folin phenol reagent.
J. Biol. Chem.
193:
265-275,
1951.
|
| 12. | Martyn, J. A. J. Basic and clinical pharmacology of the acetylcholine receptor: implications for the use of neuromuscular relaxants. Keio J. Med. 44: 1-8, 1995. [Medline] . |
| 13. | Martyn, J. A. J., D. A. White, G. A. Gronert, R. S. Jaffe, and J. M. Ward. Up-and-down regulation of skeletal muscle acetylcholine receptors. Anesthesiology 76: 822-843, 1992. [Medline] . |
| 14. | Mounsey, J. P., P. Xu, J. E. John, L. T. Horne, J. Gilbert, A. D. Roses, and J. R. Moorman. Modulation of skeletal muscle sodium channels by human myotonin protein kinase. J. Clin. Invest. 95: 2379-2384, 1995. . |
| 15. |
Murphy, B. J.,
S. Rossie,
K. S. DeJongh,
and
W. A. Catterall.
Identification of the sites of selective phosphorylation and dephosphorylation of the rat brain Na+ channel subunit by cAMP-dependent protein kinase and phosphoprotein phosphatases.
J. Biol. Chem.
268:
27355-27362,
1993.
|
| 16. |
Nudel, U.,
R. Zakut,
M. Shani,
S. Neuman,
Z. Levy,
and
D. Yaffe.
The nucleotide sequence of the rat cytoplasmic beta-actin gene.
Nucleic Acids Res.
11:
1759-1771,
1983.
|
| 17. | Pappone, P. A. Immature versus mature sodium channel forms and their responsiveness to toxins and contributions to muscle weakness. J. Physiol. (Lond.) 306: 318-320, 1980. . |
| 18. | Pavlin, E., M. Howard, and J. T. Slattery. Large burns magnify and prolong increases in acetylcholine receptors and resistance to non-depolarizing muscle relaxants in muscle under burned skin in rats (Abstract). Anesthesiology 81: A1106, 1994. . |
| 19. | Rogart, R. B., and L. J. Regan. Two subtypes of sodium channel with tetrodotoxin sensitivity and insensitivity detected in denervated mammalian skeletal muscle. Brain Res. 329: 314-318, 1985. [Medline] . |
| 20. |
Ross, A. F.,
W. N. Green,
D. S. Hartmann,
and
T. Claudio.
Efficiency of acetylcholine receptor subunit assembly and its regulation by cAMP.
J. Cell Biol.
113:
623-636,
1991.
|
| 21. |
Sherman, S. J.,
J. Chrivia,
and
W. A. Catterall.
Cyclic adenosine 35-monophosphate and cytosolic calcium exert opposing effects on biosynthesis of tetrodotoxin-sensitive sodium channels in rat muscle cells.
J. Neurosci.
5:
570-576,
1985.
.
|
| 22. | Tomera, J. F., and J. A. J. Martyn. Systemic effects of single hind limb burn injury on skeletal muscle function and cyclic nucleotide levels in the murine model. Burns Incl. Therm. Injury 14: 210-219, 1988. . |
| 23. | Tomera, J. F., and J. A. J. Martyn. Mediators of burn induced neuromuscular changes in mice. Br. J. Pharmacol. 98: 921-929, 1989. [Medline] . |
| 24. | Virginio, C., and E. Cherubini. Functional expression of voltage dependent sodium channels in Xenopus oocytes injected with mRNA from neonatal or adult rat brain. Brain Res. Dev. 87: 153-159, 1995. . [Medline] |
| 25. | Ward, J. M., and J. A. J. Martyn. Burn injury-induced nicotinic acetylcholine receptor changes in muscle membrane. Muscle Nerve 16: 348-354, 1993. [Medline] . |
| 26. | Ward, J. M., K. M. Rosen, and J. A. J. Martyn. Acetylcholine receptor subunit mRNA changes in burns are different from those seen after denervation. J. Burn Care Rehabil. 14: 595-601, 1993. [Medline] . |
| 27. | Wildicks, E. F. Neurologic complications in critically ill patients. Anesth. Analg. 83: 408-419, 1996. . |
| 28. |
Witzemann, V.,
H. R. Brenner,
and
B. Sakmann.
Neural factors regulate AChR subunit mRNAs at rat neuromuscular synapses.
J. Cell Biol.
114:
125-141,
1991.
|
| 29. | Witzemann, V., and B. Sakmann. Differential regulation of MyoD and myogenin mRNA levels by nerve-induced muscle activity. FEBS Lett. 282: 259-264, 1991. [Medline] . |
| 30. | Yanez, P., and J. A. J. Martyn. Prolonged D-tubocurarine infusion and/or immobilization causes upregulation of acetylcholine receptors and hyperkalemia to succinylcholine. Anesthesiology 84: 384-391, 1996. [Medline] . |
| 31. | Yang, J. S.-J., J. T. Sladky, R. G. Kallen, and R. L. Barchi. TTX-Sensitive and TTX-insensitive sodium channel mRNA transcripts are independently regulated in adult skeletal muscle after denervation. Neuron 7: 421-427, 1991. [Medline] . |
| 32. | Zochodne, D. W., D. A. Ramsay, S. Shelley, V. Saly, and S. Moffat. Acute necrotizing myopathy of intensive care: electrophysiological studies. Musle Nerve 17: 285-292, 1994. . |
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  C. Ibebunjo and J. A. J. Martyn Thermal Injury Induces Greater Resistance to d-Tubocurarine in Local Rather than in Distant Muscles in the Rat Anesth. Analg., October 1, 2000; 91(5): 1243 - 1249. [Abstract] [Full Text] [PDF]
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 R. R. Gomes Jr. and F. W. Booth Expression of acetylcholine receptor mRNAs in atrophying and nonatrophying skeletal muscles of old rats J Appl Physiol, November 1, 1998; 85(5): 1903 - 1908. [Abstract] [Full Text] [PDF]
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